Most of us are used to seasons. Each year, spring follows winter, which follows autumn, which follows summer, which follows spring. And winter is colder than summer. But the earth goes through temperature cycles over much longer periods than those that we experience. Between 65,000 and 35,000 years ago, the planet was much colder than it is now. During that time the temperature also changed a lot, with periods of warming and cooling. Ice melted during the warm periods, which made sea levels rise. Water froze again during the cold periods.
A new study from Switzerland, sheds light on where ice sheets melted during the ice age. It now seems that the ice melted at both ends of the earth, rather than just in either northern or southern regions.
This surprised the researchers from the University of Bern. Scientists have long assumed that most of the ice that melted was in the Northern hemisphere(半球) during the 30,000-year long ice age. That belief was held because the North Pole is surrounded by land, while the South Pole is surrounded by the Antarctic Ocean. It is easier for ice sheets to grow on land. If surrounded by sea the ice can easily just slip into the ocean instead of building up.
The researchers used a puter model to look at ways the ice could melt and how it might affect sea levels. They pared these results to evidence of how temperatures and currents actually changed during that time. The model showed that if it was only in the Northern hemisphere that ice melted, there would have been a bigger impact(影响) on ocean currents(洋流) and sea temperatures than what actually happened. Studies suggest that melting just in the Southern hemisphere would have been impossible, too. The only reasonable conclusion, the scientists could make, was that ice melted equally in the North and the South.
It is still a mystery as to what caused the temperature changes that caused the ice to melt.
【小题1】The North Pole is surrounded by land, while the South Pole is surrounded by the Antarctic Ocean. So scientists thought that . A．most of the ice melted in the Northern hemisphereB．most of the ice melted in the Southern hemisphereC．The North Pole is colder than South PoleD．The South Pole is colder than North Pole【小题2】We can infer from the passage . A．the ice can easily just slip into the oceanB．volcanoes caused the ice to meltC．melting just in the Northern hemisphere would have been impossibleD．researchers often use the puter models help their research work.【小题3】The scientists are not sure . A．how long the ice age lastedB．where ice sheets melted during the ice ageC．what caused the temperature changesD．what the earth is made up of【小题4】Which of the following is the best title for the passage?A．A puter modelB．Studies show ice melted equally in the North and the South during the ice age C．Most of the ice melted in the Northern hemisphere during the 30,000-year long ice age.D．A survey resultA
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(答案→)A
解析：
【小题1】细节题。根据第 3 段第 2,3 句 scientists have long assumed that most of the ice that melted was in the northern hemisphere during the 30,000-year long ice age. that belief was held because the north pole is surrounded by land… 可知答案。选A。
【小题2】推理判断题。根据第 4 段最后两句可 studies suggest that melting just in the southern hemisphere would have been impossible, too. the only reasonable conclusion… 可知冰川既不可能只在南半球融化，也不可能只在北半球融化。故答案为 C。
【小题3】细节题。根据文章最后一句 it is still a mystery as to what caused the temperature changes that caused the ice to melt 可知科学家们现在还没有找到引起温度变化的原因。选C。
【小题4】主旨大意题。根据主题句 ice melted equally in the north and the south 可知本文主要讲的一个新的科学发现：冰川时期的冰川融化是在南北极均匀进行的。选B。